BH, to the extent that your critique of a horse’s running is to gauge its potential for the future, then “yes” we should view that performance more sympathetically if we judge that its overall performance has been adversely affected by a mistake rather than by its innate ability. The fact that we might say that we could only rely on it running to its innate ability 4 times out of 10 because it is prone to such mistakes is a different story. If that makes sense?